Final answer:
The nurse should first assess the patient's blood pressure and heart rate to gather immediate information about their cardiovascular and respiratory status, and to rule out serious complications such as a pulmonary embolism. Therefore, the correct option is b.
Step-by-step explanation:
When a patient develops marked dyspnea and anxiety two days after undergoing pelvic surgery, the first action that the nurse should take is to assess the patient's blood pressure and heart rate. This is an immediate assessment that can provide critical information about the patient's cardiovascular and respiratory status, which may be compromised. It is necessary to rule out potentially serious postoperative complications such as a pulmonary embolism or a heart problem. The nurse should use a pulse oximeter to determine if the patient has hypoxemia, listen for abnormal sounds in the heart and lungs with a stethoscope, and should observe for any signs of distress or changes in mental status. Once urgent assessments are done and the findings documented, notifying the healthcare provider immediately is crucial, particularly if any abnormalities are found.